A capacitance type sensor is used as a device for converting magnitude and direction of a force applied by an operator into electric signal. For example, a device incorporating the capacitance type force sensor for inputting operation of multidimensional direction is used as an input device of game console (a so-called joystick).
A capacitance type sensor can be used to input an operation having a specified dynamic range as a magnitude of a force applied by an operator. It can also be used as a 2-dimensional or 3-dimensional sensor capable of dividing an applied force into respective dimensional components, for force detection. Among others, a capacitance type force sensor having a capacitance element formed by two electrodes to detect an applied force on the basis of changes of capacitance values caused by variations of distance between the electrodes is now in practical use in a variety of fields in terms of the advantage that the structure can be simplified to reduce costs.
For example, Japanese Laid-open (Unexamined) Patent Publication No. Hei 7(1995)-200164 discloses a capacitance type force sensor 510 as shown in FIG. 22. The capacitance type force sensor 510 has a substrate 520, an elastic rubber plate 530 disposed over the substrate 520, an electrode part 540 disposed on a lower surface of the elastic rubber plate 530, an electrode part 500-504 arranged on an upper surface of the substrate 520 (See FIG. 23), a presser plate 560 for fixedly supporting the elastic rubber plate 530 to the substrate 520, and an electronic device 580 arranged on a lower surface of the substrate 520. The electrode part 500-504 comprises four electrodes 501-504 arranged to be symmetric with respect to an origin, and an annular electrode 500 arranged around the outside of those electrodes, as shown in FIG. 23. The periphery of the electrode part 540 is in contact with the electrode 500 connected to ground and thus is connected to ground through the electrode 500.
When an operator presses down the elastic rubber plate 530, the electrode part 540 is displaced downwardly increasingly with the displacement force, so that the distances between the electrode part 540 and the four electrodes 501-504 are changed. Then, the capacitance values of the capacitance elements formed between the four electrodes 501-504 and the electrode part 540 are changed. By detecting the changes of the capacitance values, magnitude and direction of the force applied by the operator can be recognized.
However, the force sensor 510 shown in FIGS. 22 and 23 has the disadvantage that although when an operator presses down the elastic rubber plate 530, the electrode part 540 is displaced downwardly with the pressing force, since the amount of displacement of the electrode part 540 varies substantially in proportion to the pressing force, the operator is not given a pronounced click feeling virtually. Accordingly, the operator often carries out the operation without feeling that he/she is actually carrying out the operation. The operator cannot easily comprehend that he/she is actually carrying out the operation, unless he/she visually recognizes the operation of an operated object of the force sensor 510.
Accordingly, it is the object of the present invention to provide a capacitance type sensor that can make it easy for an operator to sensuously comprehend that he/she is actually carrying out the operation.